Selected Quarterly Financial Data (Details) - USD ($) $ / shares in Units, $ in Millions	3 Months Ended								12 Months Ended
	Dec. 31, 2017	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2016	Sep. 30, 2016	Mar. 31, 2016	Jun. 30, 2015	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Selected Quarterly Financial Data [Line Items]
Total revenues	$ 41,326	$ 36,451	$ 39,853	$ 39,146	$ 38,654	$ 35,943	$ 37,718	$ 39,485	$ 156,776	$ 151,800	$ 149,558
Income before income taxes	1,889	1,757	2,259	2,243	(1,117)	1,387	3,651	2,875	8,148	6,796	10,252
Net Income (Loss) Available to Common Stockholders, Basic	$ 2,409	$ 1,564	$ 2,042	$ 1,587	$ (783)	$ 957	$ 2,452	$ 1,970	7,602	4,596	7,373
Basic Common and Class B per share income from continuing operations	$ 0.61	$ 0.39	$ 0.51	$ 0.40	$ (0.20)	$ 0.24	$ 0.62	$ 0.50
Diluted Common and Class B per share income from continuing operations	$ 0.60	$ 0.39	$ 0.51	$ 0.40	$ (0.20)	$ 0.24	$ 0.61	$ 0.49
Material unusual or infrequently occurring items: [Abstract]
Remeasurement Gain/(Loss)					$ (3,000)
Current Federal Tax Expense (Benefit) related to Tax Cuts and Jobs Act	$ 398
U.S. Tax Legislation on Foreign Currency Gains Losses On Non-U.S. Branch Operations [Member]
Material unusual or infrequently occurring items: [Abstract]
Deferred income tax expense/(benefit) and income tax credits					$ (300)				300
UNITED STATES | Pension Plan [Member]
Material unusual or infrequently occurring items: [Abstract]
Remeasurement Gain/(Loss)									538	(900)	(1,964)
Defined Benefit Plan, Net Periodic Benefit Cost (Credit), Gain (Loss) Due to Settlement and Curtailment									354	0	0
Non-US [Member]
Selected Quarterly Financial Data [Line Items]
Income before income taxes									$ 3,298	$ 1,530	$ 4,878
Material unusual or infrequently occurring items: [Abstract]
Current Income Tax Expense (Benefit)	$ 484